Enter the first day of your last period
This uses Naegele’s rule (LMP + 280 days) to estimate your due date.
How to use the Pregnancy Due Date Calculator
- Select the first day of your last menstrual period.
- Click Calculate Due Date.
- See your estimated due date and current weeks pregnant.
- Use the Copy or Share buttons to save or send your result.
Tip: This is an estimate based on a standard 28-day cycle — your doctor may adjust it based on an ultrasound.
Common mistakes to avoid
- Entering the conception date instead of the first day of your last period.
- Treating this estimate as a guaranteed delivery date.
- Not accounting for irregular cycles, which this calculator assumes are standard.
How the due date is calculated
Naegele’s rule
This tool uses Naegele’s rule: Due Date = LMP + 280 days (40 weeks). This assumes a standard 28-day menstrual cycle with ovulation on day 14.
When to use this tool
Useful for early pregnancy planning and getting a rough estimate before your first prenatal ultrasound confirms a more precise date.
✓ Pros
- Works instantly, right in your browser
- Shows current weeks pregnant, not just the due date
- No sign-up, no ads blocking the result
✕ Limitations
- Assumes a standard 28-day cycle
- Not a substitute for ultrasound dating
- Actual delivery dates commonly vary by 1-2 weeks either way
Pregnancy Trimester Reference
How pregnancy weeks map to trimesters.
| Trimester | Weeks | Notes |
|---|---|---|
First | Weeks 1–12 | Early development |
Second | Weeks 13–27 | Often called the "easier" stage |
Third | Weeks 28–40 | Final growth stage before birth |
Enter your exact LMP date above to see your current week and trimester.
Features
Due date + current week
Instant results
No data stored
Mobile friendly
How TickmarkTools compares
An honest, feature-by-feature look at browser-based calculator tools.
| Feature | TickmarkTools | Typical free sites | Premium suites |
|---|---|---|---|
| Price | Free | Free / freemium | Free tier + paid plans |
| Sign-up required | No | Often yes | Yes |
| Data leaves your device | Never | Usually | Usually |
| Watermark on export | None | Sometimes | On free tier |
| Mobile friendly | ✓ | Varies | ✓ |
| Works without account | ✓ | Varies | ✗ |
These are general, illustrative observations about common patterns across free online calculator tools as a category — not verified or benchmarked data about any specific named competitor or product. Individual sites vary and may differ from what's shown here.
Why you can trust this tool
No data stored
Your input is never saved or logged.
Secure processing
All processing happens client-side in your browser.
Fast processing
Results render in milliseconds, no waiting.
Mobile friendly
Use this tool from any device.
No sign-up
No account, no email, no watermark.
Works offline*
Once loaded, this tool needs no internet connection.
Accuracy & limitations
This calculator is built for speed and accuracy, but it's worth understanding what it does and doesn't account for:
- Standard cycle assumption. This calculation assumes a 28-day cycle — shorter or longer cycles will shift the actual due date.
- Not medical dating. An early ultrasound provides more precise dating than LMP-based calculation alone — always confirm with your doctor.
- Delivery date varies. Only a small percentage of babies are born exactly on their estimated due date — delivery within 1–2 weeks either side is common and normal.
Pregnancy Due Date Calculator FAQ
Yes, the Pregnancy Due Date Calculator is completely free with no sign-up required.
No — all calculations happen locally in your browser, and nothing is saved or shared.
It’s a standard estimate based on Naegele’s rule — an ultrasound from your doctor typically provides more precise dating.
This calculator assumes a standard 28-day cycle — if yours is different, your doctor can adjust the estimate accordingly.
No, this is an informational estimate only — always follow up with a healthcare provider for proper prenatal care.
No. All calculations run entirely in your browser, and nothing you enter is ever sent to a server or stored.
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